In the 5th U.S. Infantry, stationed with General Zachary Taylor’s army on the Mexican border in 1846, Sergeant John Riley was rated a good soldier. Before his present duty he had served as a drillmaster for the Corps of Cadets at West Point which demanded high competence. Such was Riley’s ability that he was in line for a lieutenant’s commission, and rising from the ranks was rare at that period. He hail only one apparent fault, a grave one. He could enforce discipline but found it hard to take.

Soon after a reprimand from his captain for disobedience of orders, the smoldering Riley asked for a pass to attend Mass. He never reported back. The American Army had lost an able infantry sergeant. Mexico and General Santa Anna would gain a top artillery commander.

Riley joined the stream of deserters crossing over to the Mexicans, defections causing Zach Taylor considerable concern. They included others of the numerous foreign-born, many of them recent immigrants, who wore the blue—Irish, German, English, French, Polish. The Mexican Government had assiduously been urging all of doubtful loyalty or otherwise disaffected “to abandon their unholy cause and become peaceful Mexican citizens.” Bounties and land grants of 320 acres, rising with the deserter’s rank, were promised rewards. Impetus was added by harsh discipline in units of the U.S. Army where flogging was legal. Riley, like many other Irishmen, may well have been irked by the strong anti-Irish sentiment then prevalent in the United States.

But he and others who deserted before and alter the commencement of hostilities also met with contemptuous treatment in Mexico at first. This was wartime, and “peaceful Mexican citizens” were not desired. It was when the former sergeant organized his fellow turncoats into the San Patricio Battalion, ready to fight for their adopted country, that they began to win respect.

The San Patricios also were called the Colorados or “Red Company” because many of them were redheaded. Though they carried a banner blazoned on one side with a figure of St. Patrick and on the other with a harp and the arms of Mexico, only a proportion was Irish or Roman Catholic. They were composed of half a do/en nationalities, besides native Americans, and came from every branch of the service: infantry, cavalry, and artillery.

The last was Riley’s choice for the San Patricios. Equipped by Santa Anna’s order with heavy fieldpieces, he and the veteran artillerymen among the deserters trained the rest into crack gun crews.

The San Patricios manned Mexican guns in the stubborn defense of Monterrey whose storming cost the Americans heavy casualties. When the city yielded after a three-day battle, and the garrison marched out under the terms of capitulation, the deserters were recognized by former comrades and jeered and hissed. Silent and sullen, Riley and his men glared back. They would soon find an opportunity to take revenge for the scorn heaped upon them.

At Buena Vista on February 23, 1847, the San Patricios again stood prepared for action. Their 18and 24-pounders, emplaced to rake the plateau, formed part of General Santa Anna’s imposing array: other ready batteries, deep columns of infantry, long ranks of splendid lancers. General Taylor in nondescript civilian clothes lounged in the saddle of Old Whitey and watched out the spectacle before he gave the order to attack.

From the high ground the guns of the San Patricios opened, and battle flamed across the plateau. Lieutenant John Paul Jones O’Brien of Captain John M. Washington’s light battery—“D,” 4th Artillery—kept his “Bulldogs,” as he called his guns, barking. They hurled roundshot, then shifted to grape and canister to blast back charges by the Mexican lancers. Riley’s expert gunners retaliated by cutting up a squadron of the First Dragoons. The advantage of position and weight of metal lay with the Mexican guns, and the San Patricios, inflicting bloody losses on their former comrades, beat back the blue waves and concentrated on O’Brien. Most of his crews down around the smoking pieces, his horses killed, he stood and fought it out unsupported. His “Bulldogs” hung on until advancing enemy drove back survivors of the battery and captured its two guns not disabled.

Braxton Bragg’s flying battery, whirling up into action at a headlong gallop, began the turning of the tide. Obeying Zach Taylor’s command, “Double-shot your guns and give ‘em hell!” (let the shade of Old Rough and Ready stand absolved of the traditional, mild “A little more grape, Captain Bragg"), the artilleryman directed a hot and rapid fire that routed the Mexicans. Victory swept across the field. In Santa Anna’s retreat, the San Patricio Battalion carried off O’Brien’s two bronze 6-pounders.

After General Winfield Scott bombarded Vera Cruz into surrender and pushed on into the interior, Colonel Ethan Alien Hitchcock recruited a counterforce to the San Patricios. At Puebla he found a weaver named Manuel Dominguez who, robbed by a Mexican officer, had left his trade to become a bandit chief. Hitchcock organized Dominguez and his band as the Spy Company, officered by Americans. Raffishly uniformed in green cavalry jackets and pantaloons, trimmed with red, and straw sombreros with red streamers, they proved extremely useful as scouts and in carrying messages through the lines and were often assigned to secret missions out of uniform. Paid $25 a month and furnished arms, rations, and clothing, they were guaranteed safe passage with their families to the United States or a neutral country after the war. As Scott’s army fought its way toward the capital, the Spy Company rode with it.

It was on the second day of the Battle of Padierna or Contreras, August 20, 1847, that the Americans again met O’Brien’s “Bulldogs.” After the costly repulse of an attempt to cross the lava bed on the 19th, a brilliant flanking movement around the enemy left brought a blue brigade, supported by Captain Simon Drum’s battery, 4th Artillery, down on the Mexican rear in an overwhelming attack. In a close-up duel with Mexican artillerymen, stubbornly standing to their guns, Drum recognized their two bronze pieces as O’Brien’s. Instantly he limbered up and signaled the gallop for a stirring, hell-for-leather charge. A volley of grapeshot swept the color-bearer out of his saddle, but the flag was caught as it fell by Lieutenant Calvin Benjamin. As the head of the column crashed into the position, Drum vaulted from his saddle to lay hands on the trophies.

Although the ensuing rout of the Mexican Army reached the proportions of a panic, a hard core of veterans rallied and at Churubusco later the same day barred the American advance. There the San Patricio made its last stand.

Churubusco, derived from an Aztec word meaning Place of the War God, justified its name that day. Riley’s gunners, mainstay of the defense of the bridgehead to the massive-walled Convent of San Pablo, served their pieces with verve and fury. Their cannon smashed back assault after assault and they only yielded the bridge and retired to the convent when infantry crossed the river to outflank them and artillery enfiladed their position. To the deadly fire of the deserters, who took particular satisfaction in spotting and picking off their former officers, was attributed a large part of the considerable American losses: 137 killed, 879 wounded and 40 missing.

During the storming of the convent, which Santa Anna ordered held to the last to cover his retreat, the San Patricios fought with the utmost desperation. There was no thought of surrender among men who could feel the hangman’s noose around their necks. At last Riley and his remaining men, their ammunition exhausted, were overpowered. Seventy-five survived out of a battalion of 260; the rest, except for some who escaped, lay dead in the uniform of Mexico.

The Mexican Government would angrily term their punishment an act of Gringo barbarism, “a cruel death or horrible torments, improper in a civilized age, and for a people who aspire to the title of illustrious and humane.” Yet they were tried with scrupulous fairness, though feeling against them ran hot, and their sentences were strictly in accordance with the rules of war and the enormity of their offense. Some were acquitted as having been legitimately captured and forced into the ranks but refusing to fight. Riley and others, who had deserted before the commencement of hostilities, were sentenced to lashing and branding. Fifty were condemned to be hanged as deserters in time of war.

Ex-Sergeant John Riley, bound to a post, took his fifty lashes without a moan. But when he was branded with a “D” for deserter on the cheek bone, according to regulations “near the eye but without jeopardizing the sight,” he cried out under the agony of the redhot iron, for he suffered it twice. Since the letter was seared on upside down the first time, it was righted in a second branding.

Riley would labor as a convict as long as the army remained in Mexico. Then, head shaven, buttons stripped from the uniform he had once worn with honor, he would be drummed out of camp to the derisive fifing of “The Rogue’s March.”

Meanwhile he was forced to dig graves for the comrades who were to be executed. One group, hands pinioned and nooses around their necks, were placed in carts, driven out from under long gallows at San Angel. High drama featured the carrying out of the death sentence for the remainder. At Mixcoac they were stationed on a scaffold affording a view of the final assault on Mexico City. As American troops stormed the ramparts, the deserters watched the eagle and snake banner of Mexico lowered from its staff on Chapultepec Castle and the Stars and Stripes rise in its place. Just before the traps were sprung, with their last breath in a shout that was heard across the valley they cheered the flag they had betrayed.

For an epilogue the story of Deserters vs. Spies offers an example of national ingratitude and an instance of supreme gall.

Manuel Dominguez, leader of the Spy Company, was moved to New Orleans with his family after the war, as promised. But there, unpensioned, his services forgotten, he was left to eke out a miserable existence. The presumptuous Riley, however, dared bring suit against the United States in Cincinnati in 1849 to recompense him for damages received in his flogging and branding. The jury ruled against him.